**4. Model validation**

In order to further verify the accuracy of the numerical model established in this chapter, a heat transfer experimental platform corresponding to the HGHE was built, as shown in **Figure 9**. The verification experiment was carried out, and the measured project was compared with the simulated results, through which the verification of the model could be completed.

**Figure 9.** *Heat transfer experimental system of HGHE.*

**Figure 10.** *Comparison of simulation and experiment results.*

As can be seen from the comparison curve of inlet and outlet water temperature in **Figure 10**, the numerical simulation results are close to the experimental results, and the maximum difference is less than the 5% relative error commonly used in engineering. But the simulation results are slightly larger than the test results. In practice, there may be a series of conditions such as underground water migration, which are simplified in the model, so there are differences, but the differences are not large, resulting in the measured outlet temperature that is slightly lower than the simulated outlet temperature. In general, the operating results of the model are close to the measured values of the actual project, and the model is basically consistent with the actual values, indicating that the model is basically correct and has a certain guiding role for the actual project.
